The present invention relates to a heating element CVD system in which a heating element kept at a specified temperature is disposed in a vacuum chamber (processing container) and in which a raw material gas is decomposed and/or activated by the said heating element to deposit a thin film on a substrate placed in the vacuum chamber (processing container).
In manufacturing various kinds of semiconductor devices including a LSI (large scale integrated circuit), a LCD (liquid crystal display) and the like, a CVD (chemical vapor deposition) method has been widely used as one process for forming a predetermined thin film on a substrate
In CVD method, there are several methods, that is, a plasma CVD method in which a raw material gas is decomposed and/or activated in discharged plasma to form a thin film, a thermal CVD method in which a substrate is heated to induce a chemical reaction to form a thin film and so on. In addition, a CVD method in which a raw material gas is decomposed and/or activated by a heating element kept at a predetermined high temperature to form a thin film (hereinafter referred to as a heating element CVD method).
In a film forming system for performing the heating element CVD method (hereinafter referred to as a heating element CVD system), a heating element made of a refractory metal such as tungsten or the like is disposed in a processing chamber. The processing chamber is capable of being evacuated to a vacuum. A raw material gas is introduced into the evacuated processing chamber while the heating element is kept at high temperatures from about 1000xc2x0 C. to 2000xc2x0 C.
The introduced raw material gas is decomposed and/or activated when it passes over the surface of the heating element and reaches a substrate to deposit a thin film of the material, which is a final objective material, on the surface of the substrate. In the heating element CVD methods, a CVD method using a wire-shaped heating element is called as a Hot Wire CVD method, and a CVD method utilizing the catalytic reaction of a heating element for decomposing and/or activating the raw material gas is called as a catalytic CVD (or Cat-CVD) method.
In the heating element CVD method, the raw material gas is decomposed and/or activated when it passes over the surface of the heating element. For this reason, this method has an advantage of reducing the temperature of the substrate as compared with the thermal CVD method in which reaction is induced only by the heat of the substrate. Further, in the heating element CVD method, plasma is not produced, as it is produced in the plasma CVD method. For this reason, there is no worry that plasma causes damage to the substrate. Accordingly, the heating element CVD method is thought to be a promising candidate as a film forming method for a semiconductor device, a display device and the like of the next generation in which high integration and high functionality have been increasingly required.
FIG. 10 shows conceptional view of a conventional heating element CVD system. In a processing container 1, a predetermined processing of forming a thin film is performed to a substrate (not shown). An evacuation system 11 for evacuating the processing container 1 to a vacuum and a raw material gas supply system 21 for supplying a raw material gas into the processing container 1 for forming a thin film are connected to the processing container 1.
In the processing container 1, a heating element 3 is disposed such that the raw material gas supplied into the processing container 1 passes over the surface of it. A power supply mechanism 30 for supplying electric power is connected to the heating element 3, thereby the heating element 3 is heated and kept at a predetermined temperature (a high temperature of about from 1600xc2x0 C. to 2000xc2x0 C.) required for the heating element CVD method. Further, in the processing container 1, a gas supply unit 2 and the heating element 3 are arranged facing each other.
Further, in the processing container 1, a predetermined thin film is formed on the substrate (not shown) by the raw material gas decomposed and/or activated by the heating element 3 that is kept at the predetermined high temperature described above. For this reason, in the processing container 1, a substrate holder 4 is provided for holding the above-mentioned substrate (not shown).
In FIG. 10, it is a gate valve for carrying the substrate into or out of the processing container 1 that is denoted by a reference character 5. Further, the substrate holder 4 is provided with, as is conventionally known, a heating mechanism for heating the substrate, but this heating mechanism will not be shown or described because it is not important in the present invention.
In the embodiment shown in FIG. 10, although it is not shown, the raw material gas supply system 21 includes a cylinder filled with the raw material gas, a supply pressure regulator, a flow regulator, a supply/stop switching valve, and the like. The raw material gas is supplied by the raw material gas supply system 21 into the processing container 1 via the gas supply unit 2 provided in the processing container 1.
Further, in a process using two or more kinds of raw material gases, the raw material gas supply systems 21 of the number equal to the number of kinds of gases used are connected in parallel to the gas supply unit 2.
The gas supply unit 2, as described above, is arranged in face with the heating element 3 in the processing container 1. Further, the gas supply unit 2 has a hollow structure and many gas blowing holes 210 on a surface facing the substrate holder 4.
On the other hand, the evacuation system 11 is connected to the processing container 1 via a main valve 12 having an evacuation speed regulating function. The pressure of the processing container 1 is controlled by this evacuation speed regulating function.
In the heating element CVD method, the substrate (not shown) is a substance to be subjected to a predetermined processing of forming a thin film. This substrate (not shown) is carried in and out of the processing container 1 via the gate valve 5. And a heating mechanism (not shown) for heating the substrate (not shown) to a predetermined temperature is built in the substrate holder 4.
The heating element 3 is generally formed of a wire-shaped member and is bent in the shape of sawteeth and is held by a support body 31, the surface of which is at least made of insulator. Further, a power supply line 32 from the power supply mechanism 30 is connected to the heating element 3 by a connection terminal 33. An electric power is supplied to the heating element 3 via this connection terminal 33 to heat the heating element 3 to the predetermined temperature required for the heating element CVD method and to keep it at the predetermined temperature.
Usually, a direct current power source or an alternating current power source is used as the power supply mechanism 30. The heating element 3 is supplied with electric power from the power source and is set at the predetermined temperature by the passage of the electric current. By heating the heating element 3 to a high temperature, the raw material gas is decomposed and/or activated to effectively form a thin film.
Usually, the heating element 3 is heated to a predetermined temperature (usually, at a film forming process, a high temperature of from about 1600xc2x0 C. to 2000xc2x0 C.) by the passage of the electric current, so a refractory metal is used as the material for the heating element 3 and, in general, tungsten is used.
A case where a silicon film is formed and a case where silicon nitride film is formed are explained as examples of forming a thin film by the heating element CVD system shown in FIG. 10. The processes are proceeded as follows.
First, a mixed gas of silane (SiH4) and hydrogen (H2) is used in the case where the silicon film is formed. A mixed gas of silane and ammonia (NH3) is used in the case where the silicon nitride film is formed. The pressure in the processing container 1 is about from 0.1 Pa to 100 Pa. In both cases, the temperature of the heating element 3 is set at a predetermined temperature (usually, a high temperature of about from 1600xc2x0 C. to 2000xc2x0 C. at a film forming process), and the temperature of the substrate (not shown) held by the substrate holder 4 is set at a temperature of about from 200xc2x0 C. to 500xc2x0 C. by a heating mechanism (not shown) in the substrate holder 4.
In the case where the silicon film or the silicon nitride film is formed under predetermined film forming conditions by the use of a conventional heating element CVD system described above, the following phenomenon is produced. A refractory metal used for the heating element, for example, a tungsten wire described above or the like sometimes reacts with the silane gas to form a silicon compound (hereinafter referred to silicidation).
A silicidation mentioned above proceeds from near a connection terminal 33 that is the connection part by which electric power is supplied from the power supply mechanism 30 (that is, the connection region of the heating element 3). In the said connection region of the heating element 3, the temperature becomes lower than 1600xc2x0 C. even at the film forming process. Further, in the said connection region of the heating element 3, the reaction speed of the raw material gas with the heating element 3 is faster than the desorption speed of decomposed and/or activated gas species of the raw material gas and raw material gas itself.
The above-mentioned silicidateion changes the composition and diameter of the heating element 3 and reduces the resistance thereof. As a result, the heating power is reduced and the whole heating element is finally deteriorated. Also, it reduces a film forming speed as hours of use of the heating element is elongated. Further, since the products of the silicide and the like have high vapor pressures in general, they contaminate the deposited film and degrade the quality of the silicon film formed or the silicon nitride film formed as the deterioration of heating element is proceeding.
Therefore, it is necessary to break the vacuum in the processing container 1 to the atmospheric pressure and to change the heating element 3 when a predetermined number of substrates are processed. This change of the heating element 3 results in a problem in productivity.
As to this silicidation phenomenon, A. H. Mahan et al. made a presentation of a detailed paper entitled xe2x80x9cThe influence of W filament alloying on the electronic properties of HWCVD deposited a-Si:H filmsxe2x80x9d in Materials Research Society 2000 Spring Meeting held at Marriott Hotel and Argent Hotel in San Francisco in the U.S.A. from Apr. 24 to 28, 2000.
As to means for controlling the deterioration caused by the silicidation of the heating element, Mahan et al. proposed means for elongating the life of the heating element in the paper, that is, heating the heating element in a hydrogen gas or in a vacuum after forming a film.
However, this means needs to secure a time for performing the processing between the formations of the respective films and hence results in a problem of reducing productivity. Further, to be exact, the silicidation of the heating element proceeds while the film is being formed, that is, the temperature of the heating element or a film forming environment around the heating element 3 such as the effective region of the heating element 3 for the decomposition and/or activation of the raw material gas and the like is changed while the film is being formed. For this reason, the characteristics of the film is changed (degraded) in the direction of thickness in the case when the film forming time is long.
FIG. 11 is a view to show a part of a support body 31 of a conventional embodiment. In the part of a support body 31 of the conventional embodiment, the heating element 3 is supported by the support body 31 by means of a wire 34 (usually, made of molybdenum) to reduce a contact area of the heating element 3 thereby reducing thermal conduction. The conventional embodiment shown in FIG. 11 is intending to prevent silicidation, which proceeds from the portion of the heating element 3 where its temperature is slightly low.
However, even in this method, the temperature of the heating element 3 at the portion in contact with the wire 34 drops inevitably, so that the silicidation at and from the said portion is caused, depending on film forming conditions such as a high silane gas pressure in case of forming the silicon film or the like.
Further, even in this method, it is impossible to eliminate connection to the power supply line 32, so that the silicidation is also caused at the portion of the connection terminal 33 as is the case shown in FIG. 10.
Therefore, even in a heating element CVD system adopting the constitution shown in FIG. 11, it is necessary to break the vacuum in the processing container 1 to the atmospheric pressure and to change the heating element 3 when a predetermined number of substrates are processed. The change of the heating element 3 results in a problem in productivity.
By the way, if films are repeatedly formed in the heating element CVD system, the films are deposited on the inside of the processing container and are peeled off and results in the cause of the particulate problem. The inventors of the present application proposed a method of effectively removing a film deposited on the inside of a processing container, which become an origin of particulates, and an in situ cleaning method of a heating element CVD system (Japanese Patent Application Laid-Open (JP-A) No. 2001-49436).
According to this method, a gas supply unit 2 of a conventional heating element CVD system shown in FIG. 10 is provided with a cleaning gas supply system having the same constitution as a raw material gas supply system 21, and when cleaning the system, instead of a raw material gas used in forming a film, a cleaning gas is introduced into a processing container 1 via the gas supply unit 2. That is, this is an invention characterized in that after the processing container 1 is evacuated, a heating element 3 disposed in the processing container 1 is heated to and kept at a temperature of 2000xc2x0 C. or more, and that a cleaning gas which is decomposed and or activated by the heated body 3 to produce activated species which in turn react with a deposited film to change it into a gaseous substance is introduced into the processing container 1, and that the produced gaseous substance is exhausted from the processing container 1 to remove the deposited film from the inside surface of processing chamber. This invention has been made based on findings that when the heating element 3 is kept at a temperature of 2000xc2x0 C. or more, the heating element 3 itself does not react with the cleaning gas but remains stable.
However, after the above-mentioned invention was made, it turned out that even if it was tried to keep the heating element 3 at a temperature of 2000xc2x0 C. or more, a part near the connection terminal 33, which is the connection part of power supply from a power supply mechanism 30 to the heating element 3, was low in temperature, and that the said part was etched by the cleaning gas and was gradually reduced in diameter and finally broken by the reaction of the said part with the cleaning gas. Thus, it is necessary to replace the heating element at a certain time, which results in a problem in productivity.
Further, it was found that in the case where a film was deposited on a large-area substrate of over 1 m by the use of a heating element CVD system shown in FIG. 10 and FIG. 11, there was a room for improvement in the uniformity of thickness of a thin film deposited.
In the Cat-CVD method, in the case where in order to form a film on a large-area substrate by the use of the heating element CVD system shown in FIG. 10 and FIG. 11, a conventional technique is adopted in which a sawtooth heating element 3 is supported by a large size support frame as large as a substrate, there is presented a problem that the heating element 3 is drooped by thermal expansion. That is, since the sawtooth heating element 3 is thermally expanded by about 1% when it is heated to 1800xc2x0 C., if a heating element 3 having a length of 1 m is used to form a film on a large-area substrate, the heating element 3 is drooped by 70 mm at the maximum by a thermal expansion of 1%. In the worst case, it is estimated that the heating element 3 is drooped more than the distance between the substrate and the heating element 3, which is usually set at about 50 mm. According to the inventor""s study, it is verified that the gap (distance) between the heated heating element 3 and the substrate subjected to a film forming process greatly affects the uniformity of a film thickness when the film is formed.
At present, it is prospected that the size of a next-generation glass substrate is larger than 1 m. For example, it is planned to use a large substrate of 1100 mmxc3x971250 mm for a LCD and 1000 mmxc3x97400 mm for a solar cell. In order to form a film on such a large-area substrate, it is necessary to reduce the degree of drooping of the heating element 3 caused by the thermal expansion mentioned above and to ensure the uniformity of thickness of the film formed on the large-area substrate, so that the heating element CVD system shown in FIG. 10 and FIG. 11 has a room for improvement.
In a heating element CVD system in which a raw material gas introduced into a processing container (vacuum chamber) is decomposed and/or activated by a heating element to deposit a thin film on a substrate placed in the processing container (vacuum chamber), the objects of the present invention are as follows: one object is to prevent the connection region of the heating element connected to a power supply mechanism from being degraded by the raw material gas; and another object is to prevent the connection region of the heating element connected to a power supply mechanism from reacting with a cleaning gas when a cleaning process for removing a film deposited on the inside of the processing container is proceeded.
By countermeasures mentioned above, it is the object of the present invention to provide a heating element CVD system having high productivity that can elongate the life of the heating element and realize a stable film forming environment.
Further, it is the object of the present invention to provide a heating element CVD system that can meet with a film forming on a large-area substrate having a size of im or more and can ensure a uniform film thickness even if the film is formed on such a large-area substrate.
A heating element CVD system of the present invention is constituted as follows in order to accomplish the above objects.
A heating element CVD system of the present invention is provided with a processing container in which a predetermined processing is performed to a substrate held by a substrate holder disposed therein, an evacuation system which is connected to the said processing container and evacuates it to a vacuum, a raw material gas supply system for supplying a predetermined raw material gas into the said processing container, and a heating element which is disposed in the said processing container and is supplied with electric power from a power supply mechanism and is thereby heated to high temperatures (about from 1600xc2x0 C. to 2000xc2x0 C. when a film is formed and about 2000xc2x0 C. to 2500xc2x0 C. when a cleaning process is performed). And the heating element CVD system of the present invention relates to a heating element CVD system in which the raw material gas introduced into the processing container from the raw material gas supply system is decomposed and/or activated by the heating element kept at the high temperatures to deposit a thin film on the substrate held by the substrate holder,
In this connection, the predetermined processing described above means, for example, depositing a thin film on the substrate to be processed, which is placed in the processing container, and a cleaning or removing the substance deposited on the inside of the processing container. Further, the predetermined raw material gas is determined variously according to the thin film to be deposited and, for example, in the case of depositing a silicon film, a mixed gas of silane (SiH4) and hydrogen (H2) is used as the predetermined raw material gas described above, and in the case of depositing a silicon nitride film, a mixed gas of silane and an ammonia (NH3) is used as the predetermined raw material gas described above.
The heating element CVD system of the present invention is characterized in that, in the configuration as the before described, one or a plurality of connection terminal holders is placed in the processing chamber. Each of the said connection terminal holders holds a plurality of connection terminals at a predetermined position with electrically insulating therebetween. Each of the said connection terminals connects the heating elements to the power supply mechanism electrically. The said heating elements connected to the connection terminals are supported in face with the substrate holder. And, in that, a connection regions of the heating elements connected to the said connection terminals are not exposed to a space in the processing container.
Each connection terminal holder in the above-described heating element CVD system of the present invention is a structure that is independent of the processing container and can be removed from the processing container. Further, each connection terminal holder is connected to the power supply mechanism, the raw material gas supply system, and a gas introduction system which will be described later, respectively
In the case where a substrate to be processed is not particularly large in size, it is good enough to place one connection terminal holder in the processing container, but in the case where a substrate to be processed has a large area of 1 m or more, it is possible to cope with such a large-area substrate by increasing the number of connection terminal holders to be placed in the processing container. That is, even if the substrate to be processed has a large area of 1 m or more, it is possible to eliminate the need for manufacturing a single connection terminal holder that is equal to or larger than the area of the substrate to be processed. On the contrary, it is possible to circumvent such restriction on the arrangement of the heating element that is restricted according to the shape and size of a supporting body in the conventional art. Further, it is possible to arrange the heating element at any position of the connection terminal holder and to make a wire shaped heating element suitable length, in each connection terminal holder. For this reason, it is possible to reduce the degree of drooping of the heating element caused by thermal expansion.
In the above description, one or a plurality of connection terminal holders is placed in the processing chamber. Each of the said connection terminal holders holds a plurality of connection terminals at a predetermined position with electrically insulating therebetween. Each of the said connection terminals connects the heating elements to the power supply mechanism electrically. The said heating elements connected to the connection terminals are supported in face with the substrate holder. By the use of the said connection terminal holder, it is possible to arrange the heating elements adequately at more preferable position, and thus to form a thin film having a uniform film thickness.
In particular, even in the case where a plurality of connection terminal holders are disposed to form a thin film on a large-area substrate having a size of 1 m or more, it is possible to form the thin film having a uniform film thickness on the large-area substrate. This is because it is possible to suitably arrange the heating elements at a more preferable positions in accordance with an area of substrate to be processed, process condition, or the like in order to improve the uniformity of the thin film at the boundary region between the neighboring connection terminal holders and at the peripheral portion of the large-area substrate.
Further, even in the case where a film is formed on the large-area substrate having a size of 1 m or more, it is only necessary to dispose a plurality of connection terminal holders each of which is an independent structure, as described above. For this reason, it is possible to manufacture one connection terminal holder at low cost in such a size as improves workability and is easy to machine. Even if a substrate on which a film is formed is large in size, it is possible to easily form the film on such large-area substrate by arranging the plurality of connection terminal holders. Further, it is possible to improve the work efficiency of maintenance such as dismounting or mounting the connection terminal holders for repair in the processing container.
Next, in the heating element CVD system of the present invention, as described above, the connection region of the heating element connected to the connection terminal to connect the heating element to the power supply mechanism electrically is not exposed to the space in the processing container. Thus, it is possible to prevent the raw material gas such as silane or the like from contacting a region of the heating element where temperature is slightly low (the connection region of the heating element connected to the connection terminal) This can prevent the region of the heating element where temperature is slightly low from being degraded (changed to a silicide) by the raw material gas when the film is formed.
The structure for preventing the connection region of the heating element to the connection terminal from being exposed to the space in the processing container can be realized, for example, by the preferred embodiment described in the following.
In the first preferred embodiment, the connection region of the heating element to the connection terminal is covered with a cylindrical body or a plate which is made of an insulating substance, a metal, or a composite of these materials and covers the said connection region with a gap between the cylindrical body or the plate and the heating element.
In the second preferred embodiment, the connection region of the heating element to the connection terminal is covered with a cylindrical body or a plate that is made of an insulating substance, a metal, or a composite of these materials and covers the connection region with a connection terminal inside hollow portion between the cylindrical body or the plate and the connection terminal and with a gap between the cylindrical body or the plate and the heating element.
In the third preferred embodiment, the connection terminal is constituted by a connection terminal body and a cap put on the said connection terminal body with a gap between itself and the heating element, and a connection terminal inside hollow portion is formed between the cap and the connection terminal body.
In any one of the preferred embodiments described above, it is possible to prevent the connection region of the heating element to the connection terminal from being exposed to the space in the processing container. Thereby, it is possible to prevent the connection region of the heating element (that is, the part of the heating element where temperature is slightly low) from contacting the raw material gas or the activated species originated from the raw material gas when the film is formed and from contacting a cleaning gas when a cleaning process is performed.
In this connection, in place of the cylindrical body, it is also possible to use a plate having a hole corresponding to the hollow portion of the cylindrical body and a thickness corresponding to the length of the cylindrical body. And, it is possible to produce the same working and effect by using the said plate with covering the connection region of the heating element connected to the connection terminal and without contacting the heating element.
In the before described structure, as the hole of the cylindrical body or the plate is smaller in inside diameter and longer in length, the connection region of the heating element can be prevented more effectively from being exposed to the space in the processing container. That is, it is preferable from the viewpoint of preventing the connection region of the heating element from contacting the raw material gas when the film is formed that the hole of the cylindrical body or the plate is smaller in inside diameter and longer in length. Hence, in consideration of manufacturing accuracy and manufacturing cost, for example, in the case where a tungsten wire of 0.5 mm in diameter is used as a heating element, it is preferable that the inside diameter of the cylindrical body or the plate is about from 0.7 mm to 3.5 mm and the length thereof is about from 10 mm to 50 mm.
The above-described cylindrical body or plate is heated at a high temperature by the radiation from the heating element. Hence, it is desired that the above-described cylindrical body or plate is formed of a material having as low a vapor pressure as possible, for example, a refractory metal such as tantalum, molybdenum or aluminum. Further, it is thought that the above-described cylindrical body or plate is made of a metallic material and is directly attached to a member (for example, a plate) for holding a member to which the heating element is connected (for example, the connection terminal body or the like). In this case, there is a possibility that the said plate, etc. is put into contact with the heating element by thermal strain and the like so as to develop an electric short circuit. Hence, to prevent such electric short circuit, it is desirable that the above-described cylindrical body or plate is formed of a composite material covered with an insulating material such as aluminum or the like.
Further, it is possible to cover the connection region of the heating element to the connection terminal in the form without contacting with the said connection region. That is, the connection region of the heating element to the connection terminal is covered with the above-described cylindrical body or plate with a gap between the above-described cylindrical body or plate and the connection terminal and with a gap between the above-described cylindrical body or plate and the heating element. In this manner, it is possible to adopt a structure in which the connection region of the heating element to the connection terminal is not exposed to the space in the processing container and in which a purge gas is flowed through the gap described above from the connection terminal to the processing container.
Thereby, it is possible to further effectively prevent the connection region of the heating element where temperature is slightly low when the film is formed from being degraded (changed to a silicide) by the raw material gas. Further, when the deposited film is removed (a cleaning process is performed), it is possible to further effectively prevent the part of the heating element (connection region of the heating element) where temperature is slightly low from contacting and reacting with (being etched by) the cleaning gas.
This can be realized by adopting the following embodiment.
For example, each connection terminal holder has the first inside hollow portion, and the connection region of the heating element connected to each of a plurality of connection terminals held at a predetermined position of the connection terminal holder in an electrically insulated state is covered with a cylindrical body or a plate made of an insulating material or a metal or a composite material of these materials, which covers the said connection region of the heating element with the connection terminal inside hollow portion between the cylindrical body or the plate and the connection terminal and with a gas passing hole between the cylindrical body or the plate and the heating element, and the connection terminal inside hollow portion communicates with the said first inside hollow portion to which a gas supply introduction system for introducing gas is connected.
Alternatively, each connection terminal holder has the first inside hollow portion, and each of a plurality of connection terminals held at a predetermined position of the connection terminal holder in an electrically insulated state is constituted by the connection terminal body and a cap put on the said connection terminal body with a gas passing hole between the cap and the heating element, and a connection terminal inside hollow portion is formed between the cap and the connection terminal body, and the connection terminal inside hollow portion communicates with the said first inside hollow portion to which a gas supply introduction system for introducing gas is connected.
In any one of the preferred embodiments described above, the connection terminal inside hollow portion communicates with the space in the processing container through the gas passing hole.
Therefore, the gas or the mixed gas (purge gas) introduced into the, first inside hollow portion of each connection terminal holder from the gas introduction system is introduced into the processing container through the connection terminal inside hollow portion and the gas passing hole.
Thereby, it is possible to prevent the raw material gas such as silane gas or the like or the activated species originated from the raw material gas decomposed and/or activated on the surface of the heating element from entering into the connection terminal inside hollow portion. That is, it is possible to effectively prevent the raw material gas or the like from contacting a portion of the heating element where temperature is slightly low (connection region of the heating element). Further, also when the deposited film is removed (the cleaning process is performed), it is possible to prevent the cleaning gas from entering into the connection terminal inside hollow portion. That is, it is possible to effectively prevent the gas or the like from contacting the portion of the heating element where temperature is slightly low (connection region of the heating element).
In other words, thereby, it is possible to prevent the portion of the heating element where temperature is slightly low (connection region of the heating element to the connection terminal) from being degraded (changed to a silicide) by the raw material gas when the film is formed and from reacting with (being etched by) the cleaning gas when the deposited film is removed (the cleaning process is performed).
Here, the above-described cylindrical body, plate, and cap are arranged without contacting the heating element and the heating element is supported only by the connection terminal. Further, gas other than the raw material gas or the cleaning gas is flowed to eliminate the effect of reverse diffusion of the raw material gas. For this reason, it is possible to prevent the heating element in its entirety from being degraded by the raw material gas and to realize a stable film forming environment when the film is formed, and to prevent the heating element from reacting with the cleaning gas when the deposited film is removed (the cleaning process is formed).
As a result, the life of the heating element is elongated to reduce the downtime of production, caused by maintenance, so that productivity can be improved.
In this connection, in the above preferred embodiment, the cap may have a cylindrical body or a plate that mounted on the said cap and covers the connection region of the heating element to the connection terminal without contacting the heating element, and is made of a insulating material or a metal or a composite material of these materials. This can induce the working and effect produced by the configuration in which the connection region of the heating element to the connection terminal is covered with the cap that is mounted on the connection terminal body in such a way as to form the connection terminal inside hollow portion between the cap and the connection terminal body and to produce the gap (for example, gas passing hole) between the cap and the heating element. Further, in addition, this can produce the same working and effect produced by the above-described configuration that enables the gas or the mixed gas introduced into the first inside hollow portion of the connection terminal holder to be introduced into the processing container through the connection terminal inside hollow portion, which communicates with the first inside hollow portion, and the gas passing hole. Further, this can produce the working and effect produced by the configuration in which the cylindrical body or plate for covering the connection region of the heating element to the connection terminal without contacting the heating element is mounted on the said cap. That is, these effects are overlapped. Therefore, it is possible to further effectively to prevent the portion of the heating element where temperature is slightly low (connection region of the heating element to the connection terminal) from being degraded (changed to a silicide) by the raw material gas when the film is formed, and from being etched by the reaction with the cleaning gas when the deposited film is removed (the cleaning process is performed).
In this respect, in the above-described preferred embodiment, the gas introduced toward the processing container from the side of the connection terminal, that is, the gas introduced into the first inside hollow portion of the above-described respective connection terminal holders may be any one gas of hydrogen, argon, helium, neon, krypton, xenon, nitrogen, or ammonia, or a mixed gas of two or more kinds of these gases.
In the heating element CVD system in accordance with the present invention described above, a connection part between the connection terminal and the power supply mechanism, or a connection part between the connection terminal and the power supply mechanism and a wiring part for electrically connecting the connection terminals may be built in the connection terminal holder.
To be more specific, each connection terminal holder may have the first inside hollow portion, and a connection part between the connection terminal and the power supply mechanism, or a connection part between the connection terminal and the power supply mechanism and a wiring part for electrically connecting the connection terminals may be arranged in the said first inside hollow portion.
This can prevent the connection part between the connection terminal and the power supply mechanism, or the connection part between the connection terminal and the power supply mechanism and the wiring part for electrically connecting the connection terminals from being exposed to the space in the processing container. Therefore, this can prevent the possibility that these parts are degraded by the raw material gas, the species decomposed and/or activated on the surface of the heating element, originated from the raw material gas, or the cleaning gas.
Further, in the heating element CVD system in accordance with the present invention, each connection terminal holder may communicate with the space in the processing container only through a plurality of gas blowing holes made in the surface on the side in face with the substrate holder, and may have the second inside hollow portion connected to the raw material gas supply system.
Thereby, the raw material gas is supplied from the raw material gas supply system to the processing container by introducing the raw material gas firstly into the second inside hollow portion, and then introducing into the processing container through the plurality of gas blowing holes. Further, the cleaning gas is also supplied to the processing container by introducing the cleaning gas firstly into the second inside hollow portion, and then introducing into the processing container through the plurality of gas blowing holes.
In this manner, the plurality of gas blowing holes for introducing the raw material gas and the like into the processing container and the heating elements form an integrated structure by the respective connection terminal holders. This eliminates the need for the support member 31 used in the conventional heating element CVD system shown in FIG. 10 and FIG. 11. The support member 31 for supporting the heating element is the part on which the film might be deposited. Thus, the elimination of the support member 31 can simplify a film forming region around the heating element and can form a film in a uniform thickness and further improve productivity even when a large-area substrate is processed.
When a film is formed, a raw material gas is introduced into the second inside hollow portions of the respective connection terminal holders, and when a cleaning process is performed, a cleaning gas is introduced into the second inside hollow portions of the respective connection terminal holders. According to the above-described structure, the first inside hollow portion is separated from the second inside hollow portion, so that the portions where the connection terminals are connected to the power supply mechanism and the connection wiring between the connection terminals are not exposed to the raw material gas and the cleaning gas in the structure.
That is, by adopting the above-mentioned structure, it is possible to prevent a connection part between the connection terminal and the power supply mechanism, or a connection part between the connection terminal and the power supply mechanism and a wiring part for electrically connecting a connection terminals from being degraded by the raw material gas existing in the space in the processing container, and further to prevent these portions, in the each respective connection terminal holders, from contacting the raw material gas and the cleaning gas, supplied to each connection terminal holder in the respective connection terminal holders and introduced into the processing container through the plurality of gas blowing holes
Still further, in the above-described heating element CVD system in accordance with the present invention, each connection terminal holder may hold a plurality of heating elements such that they are in face with the substrate holder, and the gap between at least one or more heating element of the plurality of heating elements and the connection terminal holder may be different from the gap between the other heating element and the connection terminal holder.
In this manner, it is possible to adjust the distance between the heating element and the connection terminal holder by which the said heating element is supported. That is, it is possible to adjust the distance or the gap between the substrate on which the film is to be deposited and the heating element.
Still further, each connection terminal holder may hold a plurality of heating elements such that they are in face with the substrate holder, and the distances between the neighboring heating elements of the plurality of heating elements may be different from each other in part.
In this manner, it is possible to adjust distances, so that the distances between the neighboring heating elements among the plurality of heating elements supported by the connection terminal holders may be set as wide in part, and be narrow in the other part.
Thus, as described above, it is possible to form a thin film having a uniform thickness effectively by adjusting the gap between the heating element at any position among the plurality of heating elements supported by the connection terminal holders, and the connection terminal holder, or by adjusting the distance between the neighboring heating elements among the plurality of heating elements supported by the connection terminal holders, in addition to arranging the connection terminals appropriately at desirable positions, in accordance with the area of substrate to be processed and the process conditions.
In particular, in the case where a plurality of connection terminal holders are disposed to form a film on a large-area substrate, by making the gap between the heating element and the connection terminal holder at the boundary position of the neighboring connection terminal holders which are opposed to each other across a boundary between the neighboring connection terminal holders and the gap between the heating element and the connection terminal holder which are arranged at the positions corresponding to the outer peripheral portion of the large-area substrate different from the gap between the heating element and the connection terminal holder which are arranged at the other positions, it is possible to make the film thickness uniform effectively even though the plurality of connection terminal holders are arranged.
In this connection, in the above-described heating element CVD system in accordance with the present invention, each connection terminal holder may hold a plurality of heating elements such that they are in face with the substrate holder, and the gap between at least one or more heating element of the plurality of heating elements and the connection terminal holder may be different from the gap between the other heating element and the connection terminal holder, and the distances between the neighboring heating elements of the plurality of heating elements may be different from each other in part. In this manner, it is possible to form a film having a uniform thickness effectively over a large area.